Add short form -d for --debug option. Closes #5505.
Add short form -d for --debug option. Closes #5505.

tshikaboom/geary,glebihan/geary,martinra/geary,orlandosanchez/geary,mjog/geary,jimbonator/geary,martinra/geary,orlandosanchez/geary,aatishnn/geary,jimbonator/geary,rschroll/geary,AtticHacker/geary,martinra/geary,mpdeimos/geary,robol/geary,MohamedIM/geary-unofficial,jimbonator/geary,kpiwko/geary,aatishnn/geary,emersion/geary,robol/geary,kyoushuu/geary,dominickm/Geary,glebihan/geary,AtticHacker/geary,emersion/geary,didrocks/geary,glebihan/geary,mjog/geary,githubnemo/geary,kyoushuu/geary,geekvigilante/geary,aatishnn/geary,mjog/geary,rschroll/geary,abn/geary,githubnemo/geary,githubnemo/geary,tshikaboom/geary,orlandosanchez/geary,robol/geary,dominickm/Geary,emersion/geary,AtticHacker/geary,tshikaboom/geary